Liquid coating composition for the selective transmission of light



March 27, 1951 M. R. coE 2,546,724

LIQUID COATING COMPOSITION FOR THE SELECTIVE TRANSMISSION OF LIGHT Filed April 11, 1947 A E '2 2 w 40 E 0 0 1 so 2 E 0: V 20 y- I O ANGSTROM UNIT 8 a s 8 s s n v o h z so '2 9 Lu 7 3 u n: 40 Z w O. rr 0 2o l0 I g ANGSTROM g UNITS 8 8 8 o o o 0 IQ q 9 MIX/V5 R 605,

Patented Mar. 27, 1951 UNITED A? FFEQE LIQUID CUATING CUMPOSITION FOR THE SELEQTIVE TRANSMISSION OF LIGHT Application April 11, 1947, Serial No. 740,833

7 Claims.

The present invention relates to liquid coating compositions for applying a color and light shielding coating to'normally transparent or translucent materials to impart to such materials spectral characteristics capable of absorbing substantially all wave lengths of light in the ultra violet, violet and blue regions below 4900 angstrom units as well as between 6300 and 6700 angstrom units while appreciably transmitting wave lengths of light in other regions, particularly between approximately 4900 and 6300 angstrom units.

The present application is a continuation-inpart of my prior copending application Eerial No. 406,909, filed August 14, 1941, and now matured into Patent No. 2,418,318.

As disclosed in my said original application, many commodities containing chlorophyll, haemoglobin, vitamins, enzymes and porphyrins are normally deleteriously affected by photochemical action of light, particularly those wave lengths of light of the ultra-violet, violet and blue regions (below 4900 angstrom units) as well as those wave lengths between 6300 and 6700 angstrom units. The wave lengths of light between 4900 and 6300 as well as those above 6700 angstrom units do not have the same deleterious effect upon such light sensitive commodities. In fact, these wave lengths of light between 4900 and 6300 angstrom units, as well as invisible light in the infra red region, appear to have some beneficial effect on most if not all or such commodities.

For example, flowering plants, as is well known, depend on light for the advancement of the blooming stage. When restricted to selected wave lengths of light in accordance with the invention, such advancement be controlled, i. e. delayed or lengthened to meet the intended use of or market for the flowers. For example, Easter lilies, poinsettias and other seasonal flowers may be delayed from blooming too soon by placing a sheet material, having the spectral transmission herein described, around and enclosing the bud or the whole plant.

Rubber goods are prevented from losing their elasticity and rubber tires retain their resiliency for a much longer period if wrapped with a sheet material having the spectral transmission properties herein described.

Similarly, tobacco products when protected by a packaging material or wrapper having the spectral transmission properties above stated, are protected against the decomposition of nicotine salts and hence do not rapidly or materially produce or develop volatile nicotine and other throat irritating substances.

I have found that many other commodities than those containing chlorophyll, absorb light in practically the same Wave lengths of light. This is true of meat and meat products containing blood or haemoglobin or porphyrin in varying amounts, and commodities containing enzymes and vitamins, especially carotene (pro-vitamin A) and C such as in dairy products, plant products, sea food, eggs and pharmaceuticals. I have found that these commodities and substances Which are photosensitive to certain visible and ultra violet light, retain their natural characteristics and potency when shielded from light of wave lengths below 4900 angstrom units as well as Wave lengths of light between 6300 and 6700 angstrom units.

Vegetable oils contain the pigment chlorophyll which accounts for the spectral absorption by the oil of Wave lengths of light below 4900 angstrom units as well as in the regions between 6300 and 6700 angstrom units. The color screen coating of the present invention has the property of protecting the oil from deterioration by the development of rancidity and is an improvement over that disclosed in my prior Patent No. 1,880,813 in that a higher degree of transparency is obtained by the present invention and there is provided a greater fastness to light and a color screen which is more appealing to the eye from a sales point of view.

The same chlorophyll pigment is present in unripened fruits and vegetables, as well as in the early stage of flowering plants. It is also present in rubber. In the curing of tobacco and in the preparation of tobacco products chlorophyll is also present. Chlorophyll is the photose -sitizer for the chemical action in plant life brought about in the presence of light. Haemoglobin in meat and meat products has practically the same absorption characteristics as chlorophyll and also acts as a photosensitizer when exposed to light. Vitamins and enzymes are in commodities containing porphyrins including chlorophyll and haemoglobin as well as other photosensitizers, and therefore the characteristics and potency of vitamins and enzymes are more or less controlled by the presence of such photosensitizers. Therefore, the present invention provides a color screen coating which has for its primary function the property of absorbing substantially the same wave lengths of light as are absorbed by nature in growing vegetation and in meat and meat products and other commodities containing porphyrins.

The protection of the commodities above described is advantageously cffected by employing istics.

3 a light shield for the commodity, which shield may be in the form of a plate, cap, tube, hand, bag, formed container such as bottles, cartons, boxes, packs, container linings, or sheetwvrapping materials of paper, glassine, synthetic plastics, non-fibrous cellulose materials, such as regenerated cellulose, and cellulose derivatives such as cellulose ethers and cellulose esters, and synthetic resinous plastics which may normally be transparent or translucent to light. Many of such shields are advantageously produced by coating a normally transparent or translucent body, on one or both sides, with a coating composition as herein disclosed.

The present invention relates to a coating composition, in the form of a paint or lacquer, which may be applied to one or more surfaces of the shielding or protecting material to impart to the mate ial the spectral properties of transmitting wave lengths of light of approximately 4900 to 6300 and above 6700 angstroin units while excluding therefrom approximately all other light, and particularly those wave lengths between 6350 and 6700 as well as those below 4900 angstrom units which constitute the ultra violet, violet and blue regions. In the preferred form of the invention the composition includes a phthalocyanine pigment.

As stated above, the coating composition and the resulting coated screen are transmissive of those wave lengths of light within the visible spectrum of from 4900 to 6300 which comprise generally the green, yellow and orange bands of the visible spectrum. Essentially the coating may be of a green color, but is not composed wholly of green pigments. Advantageously, the coating may be composed of a combination of a yellowand an orange pigment combined with a suitable blue or green pigment in such proportions as to produce the spectral transmission properties desired.

Most pigments employed in the liquid coating arts, which are suitable for producing the spectral transmission properties desired, are not sufficiently fast to light and hence the light transof the invention resides in the employment of a phthalocyanine pigment which I have found is substantially stable to light and considerably enhances the life and usefulness of the shield or screen.

As disclosed in my said copending application Serial No. 406,909, a suitable screen having the desired spectral absorption and transmission properties may be produced by a coating including either Malachite green, Monastrel green or Fast green (General Dyestuff 5832) combined with a suitable yellow dye or pigment. Of the above, l /ionastrel green is a phthalocyanine pigment and is preferable for light fastness and stability as well as light absorption character- The spectral transmission properties of such a coating are illustrated in Fig. 1, wherein the coating was applied to both sides of a sheet of normally transparent glassine. The spectrophotometric curve shown in Fig. 1 of the above described coating shows substantially complete absorption of all wave lengths in the ultra violet, violet and blue regions from 2 .00 angstrom units to i960 as well in the red-band from 6300 to 6700. For such regions there should not be more than 5 percent transmission, but preferably none at all. Wave lengths of light between 4900 and 6300 angstrom units are transmitted through the screen and coating in excess of 10 percent, and for most purposes it is desirable that such transmission be in the order of at least 30 percent. There is also a transmission of wave lengths of light above 6'700 angstrom units in excess of 10 percent, which is highly desirable for certain uses.

Desirably, the coating composition of the present invention may be in the form of a lacquer or a paint suitable for coating transparent or translucent bodies such as glassine, plastic sheets, transparent cellulose or glass containers, plates or panes. The phthalocyanine pigments are not alcohol soluble and should be ground and mixed with a suitable plasticizer, preferably an oil plasticizer, in order to be incorporated in a lacquer or oil vehicle.

A suitable lacquer capable of producing a spectral transmission according to the invention may comprise the following:

0.85 part Azasol Fast Yellow RCA 0.10 part Azasol Fast Orange GA 0.50 part Azasol Fast Blue HLO 48.95 parts dye solvent 150.00 parts clear lacquer 1.3 parts Heliogen green GA powder 2.66 parts castor oil In the above formulae the Azasol spirit soluble dyes are well known fast dyes made and sold by General Dyestuff Corp. The Heliogen green powder is a phthalocyanine pigment that is ground and mixed with the castor oil plasticizer for incorporation into the lacquer vehicle.

In the above composition the coloring agents, comprising the dye mixture and the phthalocyanine pigment, constitute approximately 1.4 percent of the composition. The yellow dye comprises about 30 percent of the combined coloring agent, the orange dye about 4 percent and the blue dye about 9 percent thereof. While these proportions may be varied slightly they must be fairly closely controlled to produce in the coating film the desired spectral transmission properties.

Such a lacquer is suitable for coating glass and light transparent bodies, that possess spectral transmission properties substantially as described in Fig. 2, wherein there is substantially complete absorption of light below 4900 angstrom units as well as between 6300 and 6700 angstrom units accompanied by substantial transmission of those wave lengths of light between 4930 and 6300 angstrom units.

A paint suitable for glass bodies, such a containers, plates and panes, may comprise the following:

6.30 part Sudan orange ERA 150.00 parts Spar varnish 1.50 parts Heliogen green powder (ground in oil plasticizer) 3.00 parts raw linseed oil While it is possible to produce a liquid coating composition having the spectral absorption characteristics of my invention, I prefer to use one including a phthalocyanine pigment because of its fastness to light and structural similarity to porpnyrins which is the fundamental nucleus of the natural coloring matters of the chlorophyll and hemin series. Both the phthalocyanine pigments and commodities containing porphyrins possess similar spectral absorption characteristics and hence the incorporation of a phthalocyanine pigment in the coating acts to retard photosensitive deterioration in the porphyrin-containing commodities.

It is desired to be emphasized that the dyes and pigments employed in the composition are selected without'regard for the visual color effect, i. e; a green color, but rather for their light absorption characteristics in the ultra violet, violet and blue regions (i. e. 2400 to 4900 A. u.) as well as in the red region or from 6300 to 6700 A. 11. In some instances, for example as illustrated in Fig. 2, it is desirable that the transmission of light between 0700 and 7500 A. u. be not more than percent accompanied by an increased transmission of the invisible infra red above 7500 or 8000 A. u. Alternatively, for certain purposes, i. e. for the protection of plants and plant products, a higher transmission of light above 6700 A. u. is not accompanied by harmful effects.

The critical limits of the invention reside in a substantially complete absorption of all wave lengths of light in the ultra violet, violet and blue and below 4900 A. u., as well as substantially complete absorption of those wave lengths between 6300 and 6700 A. 11. By substantially complete absorption is meant that not more than 5 percent transmission takes place in thes regions,

but preferably none at all. There also should be at least a 10 percent transmission of wave lengths between 4900 and 6300 with a peak transmission, preferably of at least percent, at approximately 5500 A, u. accompanied by a substantial transmission of wave lengths above 7500 or 8000 A. u.

The coating composition of the present invention i normally a liquid composition having a lacquer, varnish or like vehicle enabling the composition to be applied to an object by usual coating methods, as for example by dipping, brushing, rolling or spraying.

It will be apparent to persons skilled in the art that the invention is not restricted to the specific examples given, which ar intended as illustrative only, but includes as well other formulae and compositions as are more fully defined in the appended claims.

I claim:

A liquid coating composition capable of being applied as a film to bodies to be coated, said composition consisting essentially of a mixture of phthalocyanine pigment with a solution of soluble dyes selected from the group consisting of yellow and orange dyes and a blue dye dissolved in a solvent dispersed in the composition vehicle in proportions not exceeding about 1.0 to 1.4 percent of the composition to impart to a film thereof the properties of substantially absorbing all wave lengths of light in the ultra violet, violet and blue regions below 4900 angstrom units and substantially between 6300 and 6700 angstrom units, and having at least ten percent transmission of light between 4900 and 6300 angstrom units, said soluble dye mixture constituting approximately from 0.2 to 0.7 percent of said composition.

2. A transparent liquid coating composition capable of being applied as a film to bodies to be coated, said composition consisting essentially of a mixture of yellow, orange and blue spirit soluble dyes dissolved in a solvent and a phthalocyanine pigment dispersed in a suitable vehicle said dye mixture constituting about 0.75 percent of said composition to impart to a film thereof the properties of substantially absorbing all wave lengths of light in the ultra violet, violet and blue regions below 4900 angstrom units and substantially between 6300 and 6700 angstrom units, and having at least ten percent transmission of light between 4900 and 6300 angstrom units, said yellow and orange dyes constituting about twothirds of said soluble dye mixture.

3. A transparent liquid coating composition capable of being applied as a film to bodies to be coated, said composition consisting essentially of a mixture of yellow, orange and blue spirit soluble dyes dissolved in a solvent and a phthalocyanine pigment dispersed in a suitable vehicle said dyes and pigment constituting about 1.4 per cent of the composition to impart to a film thereof the properties of substantially absorbing all wave lengths of light in the ultra violet, violet and blue regions below 4900 angstrom units and substantially between 6300 and 6700 angstrom units, and having at least ten percent transmission of light between 4000 and 6300 angstrom units, and said blue dye constituting approximately one-third of said soluble dye mixture.

4. A transparent liquid coating composition consisting essentially of a mixture of phthalocyanine pigment and yellow, orange and blue light fast dyes dissolved in a solvent and a lacquer vehicle for said dyes and pigment to enable the coating to be spread as a film upon a surface, said dyes and pigment constituting not more than substantially 1.4% of the composition and said yellow, orange and blue dyes constituting respectively about 0.4, 0.05 and 0.25 percent of said composition so as to impart to a film thereof the properties of substantially absorbing all wave lengths of light in the ultra violet, violet and blue regions below 4900 angstrom units and substantially between 6300 and 6700 angstrom units, and having at least ten percent transmission of light between 4900 and 6300 angstrom units.

5. A transparent liquid coating composition consisting essentially of a mixture of yellow, orange and blue spirit soluble dyes dissolved in a suitable solvent phthalocyanine pigment and a lacquer vehicle for said dyes and pigment to enable the coating to be spread as a film upon a surface, said dyes and pigment constituting not more than substantially 1.4% of the composition and said yellow, orange and blue dyes constituting respectively about 30, 4 and 9 percent of the dye and pigment components so as to impart to a film thereof the properties of substantially absorbing all wave lengths of light in the ultra violet, violet and. blue regions below 4900 angstrom units and substantially between 6300 and 6700 angstrom units, and having at least ten percent transmission of light between 4900 and 6300 angstrom units.

6. A liquid coating composition consisting essentially of a mixture of phthalocyanine pigment and a soluble light fast orange dye, and a suitable vehicle for said dye and pigment to enable the coating to be spread as a film upon a surface, said dye and pigment constituting not more than substantially 1.2% of the composition and the amount of said orange dye being not more than approximately one-fifth of said pigment component so as to impart to a film thereof the properties of substantially absorbing all wave lengths of light in the ultra violet, violet and blue regions below 4900 angstrom units and substantially between 6300 and 6700 angstrom units, and having at least ten percent transmission of light between 4900 and 6300 angstrom units.

'7. An article of manufacture comprising a normally translucent or transparent body having a transparent coating thereon formed from a coating composition consisting essentially of a mixture of yellow, orange and blue dyes miscible with the composition vehicle and a phthalocyanine pigment dispersed in a said vehicle, said dye and pigment mixture constituting from 0.7 to 1.0 percent of said film and said dye mixture being approximately two-thirds of-the combined dyes and pigments, said coating having the properties substantially absorbing allwave lengths of light in the ultra violet, violet and blue regions below 4900 angstrom units and sub stantially between 6800 and 6700 angstrom units,

and having at least ten percent transmission of light between 4900 and 6300 angstrom units. MAYNE' R. COE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. A LIQUID COATING COMPOSITION CAPABLE OF BEING APLIED AS A FILM TO BODIES TO BE COATED, SAID COMPOSITION CONSISTING ESSENTIALLY OF A MIXTURE OF PHTHALOCYANINE PIGMENT WITH A SOLUTION OF SOLUBLE DYES SELECTED FROM THE GROUP CONSISTING OF YELLOW AND ORANGE DYES AND A BLUE DYE DISSOLVED IN A SOLVENT DISPERSED IN THE COMPOSITION VEHICLE IN PROPORTIONS NOT EXCEEDING ABOUT 1.0 TO 1.4 PERCENT OF THE COMPOSITION TO IMPART TO A FILM THEREOF THE PROPERTIES OF SUBSTANTIALLY ABSORBING ALL WAVE LENGTHS OF LIGHT IN THE ULTRA VIOLET, VIOLET AND BLUE REGIONS BELOW 4900 ANGSTROM UNITS AND SUBSTANTIALLY BETWEEN 6300 AND 6700 ANGSTROM UNITS, AND HAVING AT LEAST TEN PERCENT TRANSMISSION OF LIGHT BETWEEN 4900 AND 6300 ANGSTROM UNITS, SAID SOLUBLE DYE MIXTURE CONSTITUTING APPROXIMATELY FROM 0.2 TO 0.7 PERCENT OF SAID COMPOSITION. 